This invention relates to a process for producing readily sinterable aluminum nitride powder, more particularly to a process for producing readily sinterable aluminum nitride powder which can produce a homogeneous and dense aluminum nitride sintered body without further adding a sintering aid.
A sintered body of aluminum nitride has good stability at high temperature and high thermal conductivity and its uses as useful high temperature materials are going to be developed.
Such a sintered body can be produced by, for example, molding a powdery mixture of aluminum nitride powder and a sintering aid into a molded body with a desired shape, and sintering the molded body in a predetermined atmosphere (primarily of nitrogen) at a predetermined temperature.
Provided that the molding and sitering conditions, etc. are the same, the characteristics of the sintered body will be greatly affected by various factors such as the average particle size, variance in particle sizes and shapes of the particles of the aluminum nitride powder employed as the starting powder.
Whereas, in the prior art, aluminum nitride powder has been produced by such a method as direct nitrogenation of aluminum powder or carbon reduction-nitrogenation of alumina powder. However, according to these methods of the prior art, it has been very difficult to make particle sizes smaller, to make their variance smaller and also to make particle shapes uniform.
Also, the characteristics of the sintered body will also greatly be affected by the condition of the sintering aid to be formulated at the same time (e.g. difference in powder shape and particle size between of the starting material and the additive, the state under which both the starting material powder and the additive powder are dispersed, etc.).
Further, although a method employing a ball mill, etc. is usually applied for mixing of aluminum nitride powder and powder of a sintering aid, no ideal homogeneous mixed state can be attained in mixing both powdery partners, whereby homogeneity in characteristics in a sintered body must but be unsatisfactory.